Please advice me whether a claim or promise made after the agreement can be legally binding in this case. And advise any claims A can made against B

A accept B's proposal. As they were leaving the restaurant, however, A began to have doubts about their agreement

A: 3 years is a long time to be stuck using the same product

B: All my customers are signed on for 3 years - those are the standard terms for all my contract. But look, just between friends, if it doesn't work out I'll let you out of the contract early - we'll sort it out if the time comes

Then A received the first shipment and was satisfied. However, after some time, A's customers are leaving as it seems they don't like the smell of B's products. So A want to leave the contract. B refuse